ABSTRACT Heart Failure (HF) in pediatric patients is a devastating disease that is difficult to evaluate, even with invasive hospital procedures. Importantly, and unique to the pediatric population, approximately 25% of pediatric HF patients spontaneously recover normal heart function within 1 year of diagnosis. Unfortunately, there is no reliable clinical parameter or biomarker that allows pediatric cardiologists to correctly predict which of their HF patients will recover normal heart function without surgical intervention, forcing clinicians to place their these children on transplant lists even though surgical intervention would be unnecessary in some cases. Offering a potential solution to this problem, a recent study performed at the University of Colorado Denver has identified unique expression signatures of microRNAs found in circulating blood that correlate with a subpopulation of pediatric HF patients who recover ventricular function without surgical intervention. It is the objective of this Phase I project to complete initial proof-of-concept experiments related to the development of a commercial test based on the measurement of these circulating miRNAs. The work proposed to complete this project is designed to provide the groundwork for a prospective Phase II trial. By establishing and validating the test protocols with control samples, this project will create the basis for a test that can then be evaluated in a subsequent prospective study designed to tests newly diagnosed pediatric HF patients and follow their treatment outcomes. The successful development of a non-invasive test for pediatric HF patients would have significant patient and commercial value. By providing clinicians with a non-invasive risk stratification tool for pediatric patients with HF, a test of this kind would (1) help clinicians, patients and families understand health related prognosis for appropriate long-term planning, (2) reduce the number of invasive procedures performed on these compromised patients, (3) prevent unnecessary transplantations, improving survival for decades beyond the current 10-20 year lifespan of a transplanted heart, and (4) decrease health care expenditures associated with cardiac transplantation.